Visualization and characterization of pulmonary lobar fissures

ABSTRACT

Systems and methods for visualizing pulmonary fissures including a processor and software instructions for creating a 3 dimensional model of the fissures. Creating the 3 dimensional model includes accessing volumetric imaging data of the patient&#39;s lungs, analyzing the volumetric imaging data to segment the lungs into lobes, using the segmented lobes to identify locations at which pulmonary fissures should be present where the lobes abut each other, analyzing the volumetric images to identify locations at which pulmonary fissures actually are present as existing fissure, comparing the locations at which pulmonary fissures should be present to the locations at which pulmonary fissures are present to identify locations of missing fissure, and creating a visual display comprising a 3 dimensional model of the pulmonary fissures including existing fissure portions and missing fissure portions, with the existing fissure portion visually distinct from the missing fissure portions.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.13/804,542, filed Mar. 14, 2013, which claims the benefit of U.S.Provisional Application No. 61/712,700, filed Oct. 11, 2012 and entitledVisualization and Characterization of Pulmonary Lobar Fissures, thedisclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

Embodiments of the invention generally relate to visualization andcharacterization of pulmonary lobar fissures.

BACKGROUND OF THE INVENTION

Severe emphysema is a debilitating disease that limits quality of lifeof patients and represents an end state of Chronic Obstructive PulmonaryDisease (COPD). It is believed that 3.5 million people in the US havethe severe emphysematous form of COPD, and it is increasing in bothprevalence and mortality. Current treatment methods for severe emphysemainclude lung volume reduction (LVR) surgery, which is highly invasive,and can be risky and uncomfortable for the patient. New treatmentmethods for treating emphysema include bronchoscopy guided LVR (BLVR)devices such as one-way valves that aim to close off ventilation to thediseased regions of the lung, but maintain ventilation to healthierlung. Bronchoscopy-guided techniques have the promise to be lessinvasive, less costly and more highly accurate treatments for patientswith severe disease and improve the quality of life of severe emphysemapatients.

Emphysema can present itself in various disease forms (i.e.,phenotypes). Predicting the right treatment for these patients at theappropriate time in the disease process likely depends on the phenotypeof the disease. Imaging techniques provide an in-vivo mechanism toobjectively quantify and characterize disease phenotypes and can be usedin the patient selection process for the various procedural options.Quantitative imaging biomarkers can be used to effectively phenotypedisease and therefore predict those patients most likely to respond tothe targeted treatment options. By triaging patients to the appropriatetherapy, there exists a greater promise for a positive impact on patientoutcome, reduced healthcare costs, and replacing more invasiveprocedures like LVR surgery in treating patients with severe emphysema.

Fissures are important anatomical structures within lungs. It isbelieved that fissures have an effect on regional lung mechanics. Forexample, adjacent lobes can slide against each other at fissureinterfaces, which provide a means to reduce lung parenchymal distortion.In addition, intact fissures play an important role in reducingcollateral ventilation among lobes and the spread of diseases. Recently,fissure integrity has emerged as a strong biomarker to predict theresponse to interventional emphysema therapies including localized lungvolume reduction. In short, if the fissure of the lung is intact, anobstructive device like a valve will more likely produce a seal leadingto the atelectasis (i.e., collapse) of the diseased lung sub-region.Without an intact fissure, there is a possibility of collateralventilation and the likelihood of success of the procedure may bereduced. However, accurately detecting and characterizing fissures indiseased lungs is difficult.

Methods of detecting fissures include fitting the existing portions ofthe fissures to a lobar atlas (as described in E. M. van Rikxoort etal., “A method for the automatic quantification of the completeness ofpulmonary fissures: evaluation in a database of subjects with severeemphysema.,” European radiology, (2011): 0-7, for example) or by anextrapolation of the existing portion of the fissure to the absentportion (as described in J. Pu et al., “Computerized assessment ofpulmonary fissure integrity using high resolution CT.,” Medical Physics,37(9), (2010): 4661-4672, for example). However, neither of theseapproaches makes full use of the anatomic information available in theimage data.

SUMMARY

Certain embodiments of the present invention are described in thefollowing illustrative embodiments.

Embodiments of the invention automatically detect, display and/orcharacterize fissures in diseased lungs such that the fissures mayfunction as a biomarker that is predictive of patients' response to aprocedure for treatment of emphysema and other diseases.

Some embodiments include a system for visualizing pulmonary fissures ofa patient's lungs including a processor and software comprisinginstructions for the processor for creating a visual display comprisingthe 3 dimensional model of the pulmonary fissures. Creating a visualdisplay comprising a 3 dimensional model of the pulmonary fissures mayinclude accessing volumetric imaging data of the patient's lungs,analyzing the volumetric imaging data to segment the lungs into lobes,using the segmented lobes, identifying locations at which pulmonaryfissures should be present as the locations where the lobes abut eachother, analyzing the volumetric images to identify locations at whichpulmonary fissures are present as existing fissure, comparing theidentified locations at which pulmonary fissures should be present tothe identified locations at which pulmonary fissures are present toidentify locations of missing fissure, and creating a visual displaycomprising a 3 dimensional model of the pulmonary fissures comprisingexisting fissure portions and missing fissure portions, wherein theexisting fissure portion are visually distinct from the missing fissureportions. In some embodiments, the existing fissure portions may bedisplayed in a different color than the missing fissure portions in the3 dimensional model.

In some embodiments, the software further includes instructions tocreate a graphical user interface allowing a user to reclassify alocation on the 3-dimension model of the fissure from existing tomissing or from missing to existing by interacting with the 3dimensional model on the graphical user interface.

In some embodiments, the 3 dimensional model of the fissures alsoincludes a 3 dimensional representation of the lung parenchyma incombination with the fissures. In some embodiments, the 3 dimensionalmodel of the fissures may also include a 3 dimensional representation ofa tumor in combination with the fissures, and the software may furtherinclude instructions for identifying a location of the tumor byanalyzing the volumetric imaging data. For example, the software mayinclude instructions to calculate a distance between the tumor and anearest fissure location. 13. In some embodiments, the software furtherincludes instructions for calculating the thickness of an existingfissure.

In some embodiments, the software further includes instructions forcalculating a numerical value representing integrity of the fissures.The numerical value may provide a relative proportion of amount of thefissure that exists and amount of fissure that is missing. In someembodiments, the software may include instructions for calculating anumerical value representing integrity of a portion of a fissureabutting a lobe, wherein the portion of the fissure abutting the lobe isless than the complete fissure. In some embodiments, the software mayfurther include instructions for calculating a numerical valuerepresenting integrity of a portion of a fissure abutting a sub-lobe.

In some embodiments, the software may further include instructions forreceiving directions from a user to reclassify a fissure locationidentified by the system as existing fissure to be identified anddisplayed as missing fissure in the 3 dimensional model. Alternativelyor additionally, in some embodiments, the software may further includeinstructions for receiving directions from a user to reclassify afissure location identified by the system as missing fissure to beidentified and displayed as existing fissure in the 3 dimensional model.

Other embodiments include a system for visualizing pulmonary fissures ofa patient's lungs including a processor and software includinginstructions for the processor for creating a visual display comprisingthe 3 dimensional model of the pulmonary fissures. Creating a visualdisplay including a 3 dimensional model of the pulmonary fissures mayinclude accessing volumetric imaging data of the patient's lungs,analyzing the volumetric imaging data to segment the lungs into lobesand sub-lobes, using the segmented lobes to identify locations at whichpulmonary fissures should be present where the lobes abut each other,analyzing the volumetric images to identify locations at which pulmonaryfissures are present, comparing the identified locations at whichpulmonary fissures should be present to the identified locations atwhich pulmonary fissures are present to identify locations of missingfissure, identifying portions of the present and missing fissures whichabut the sub-lobes, and creating a visual display comprising a 3dimensional model of the pulmonary fissures comprising existing fissureportions and missing fissure portions in which the existing fissureportion are visually distinct from the missing fissure portions and inwhich the portions of the missing and existing fissures abutting thesub-lobes are visually distinct from each other. For example, theexisting fissure portions may be displayed in a different color than themissing fissure portions in the 3 dimensional model. In someembodiments, the missing and existing fissures abutting the sub-lobesare each presented in a different color.

In some embodiments, the software further includes instructions forcalculating a numerical value representing integrity of the fissures, inwhich the numerical value provides a relative proportion of amount ofthe fissures that exists and amount of fissure that is missing. Forexample, the numerical value representing integrity of the fissures maybe a calculation of the integrity of an entire fissure, of only aportion of a fissure which is less than the whole fissure abutting alobe, or only a portion abutting a sub-lobe, wherein selection of theentire fissure, the portion abutting the lobe, or the portion abutting asub-lobe can be determined by a user.

In some embodiments, the software further includes instructions forreceiving directions from a user interacting with the 3 dimensionalmodel of the fissures on a graphical user interface to reclassify afissure location identified by the system as existing fissure to beidentified and displayed as missing fissure, and to reclassify a fissurelocation identified by the system as missing fissure to be identifiedand displayed as existing fissure.

Other embodiments include methods of creating a three dimensional modelof pulmonary fissures of a patient including accessing volumetricimaging data of the patient's lungs, analyzing the volumetric imagingdata to segment the lungs into lobes, using the segmented lobes toidentify locations at which pulmonary fissures should be present as thelocations where the lobes abut each other, analyzing the volumetricimages to identify locations at which pulmonary fissures are present asexisting fissure, comparing the identified locations at which pulmonaryfissures should be present to the identified locations at whichpulmonary fissures are present to identify locations of missing fissure,and displaying the three dimensional model on a display, in which thevisual display includes existing fissure portions and missing fissureportions and in which the existing fissure portion are visually distinctfrom the missing fissure portions.

Using objective, quantitative measures of disease obtained from imagingmodalities like computerized tomography (CT) in routine clinicalpractice requires providing accurate and immediate information to aphysician in a busy practice. Anatomic structural deformities in lungfissure can be more easily understood within a visual context.Embodiments of the invention therefore provide easy and immediate accessto pertinent measures of disease and enhanced multidimensional visualmodels, for easy consumption by the clinician such as the pulmonaryphysician.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of theinvention and therefore do not limit the scope of the invention. Thedrawings are not necessarily to scale (unless so stated) and areintended for use with the explanations in the following detaileddescription. Embodiments of the invention will hereinafter be describedin conjunction with the appended drawings, wherein like numerals denotelike elements.

FIG. 1 shows a flowchart of a fissure characterization and visualizationmethod associated with certain embodiments of the invention.

FIG. 2 shows a CT scan in a sagittal view in which the fissures havebeen enhanced.

FIG. 3 shows three-dimensional models of surface rendering of fissuresof an emphysema patient in accordance with certain embodiments of theinvention.

FIG. 4 a shows an example of a sagittal CT image of the right lungwithout fissures identified and highlighted in accordance with certainembodiments of the invention.

FIG. 4 b shows an example of a sagittal CT image of the right lung withfissures identified and highlighted in accordance with certainembodiments of the invention.

FIG. 5 shows an example of a screen shot including highlighting of thefissures in various two-dimensional CT images and a correspondingthree-dimensional volume rendering in accordance with certainembodiments of the invention.

FIG. 6 shows an example of three-dimensional models of a fissure (a)-(c)and of the sublobes surrounding the fissure (d).

FIG. 7 shows an example of visualization of the spatial relationshipbetween fissures and regions of emphysema in a three-dimensional modelin accordance with certain embodiments of the invention.

FIG. 8 shows an example of visualization of the spatial relationshipbetween fissures and tumors in a three-dimensional model in accordancewith certain embodiments of the invention.

FIG. 9 illustrates a fissure editing tool in use to revise theidentification of a portion of a fissure as complete or incomplete on aCT image.

FIG. 10 illustrates a fissure editing tool in use to revise theidentification of a portion of a fissure as complete or incomplete on athree-dimensional model of the fissure.

DETAILED DESCRIPTION

The invention describes a process to automate, display, interact withand characterize the fissures of the lung in multiple dimensions. Whenthe human lung is imaged in vivo with an imaging acquisition device,like CT, that image can be reconstructed and evaluated to depict normaland diseased states. Because of the various subclasses of disease andthe various depictions (phenotypes) of a disease entity, evaluation oflobular regions of the lung and the fissures separating them areimportant to accurately characterize disease and predict response toBLVR therapy.

This disclosure includes methods to provide visualization of thefissures in two and three dimensions, define the fissure boundaries,characterize their morphologic characteristics which may be used foridentifying a disease phenotype, and visualize regions of intact andmissing fissures, and observe the difference between normal and diseasedlung in an instantaneous and automated way to enable clinical decisionmaking

The left and right lungs are each divided into a plurality of lobes bydeep clefts, which are the interlobar fissures, referred to hereinsimply as fissures. The outer surface of the lungs is lined by pleura,including an inner layer which is the visceral pleura which dips intothe fissures to surround the lobes. The fissures therefore are the joinbetween the lobes of the lung and are defined by the outermost surfaceof the lobes and the visceral pleura at the locations where the lobesabut each other. Therefore, although the fissure itself is actually aninterface between abutting lobes, it is the very thin layer of the lobarinterfaces that can be detected on a volumetric image and is interpretedas being the fissure. The right lung normally includes three lobes (theupper, middle, and lower lobes) which are divided by two fissures, knownas the oblique and the horizontal fissure. The left lung normallyincludes two lobes (the upper and lower lobes) with one fissure, theoblique fissure, between them.

The edges of the lobes and the pleura that lines the lobes define thefissures and separate the lobes such that the ventilation of each lobeseparates from that of adjacent abutting lobes. In addition, the pleuranormally form a smooth surface, allowing abutting lobes to sliderelative to each other during inhalation and exhalation. However, incertain disease conditions, the pleura may become thickened or adherent.In addition, abutting lobes may adhere to each other and the pleura andlung margins that normally define the fissure may be lost. In suchlocations, the fissure is described as “incomplete,” “missing,” or“absent” and air can flow between the lobes. Various embodimentsdescribed herein identify the fissures using volumetric radiologicalimages such as CT and present them visually in 2D images or in 3D modelsfor a user such as a clinician. In some embodiments, the absent portionsof the fissures are also identified and can also be visualized, as byshowing the “absent” portions in a color which is distinct from theexisting fissures, in a location in which they would normally be presentin a complete fissure.

Various embodiments may be performed by a lung visualization system,which may include a processor, such as a processor in a computer, andmay also include a visual display such as a monitor or screen. Thesystem may also include instructions included in software (computerreadable media), stored in memory of the system, and operable on theprocessor. The software may include instructions for the processor toperform the various steps and methods described herein, includinginstructions to receive patient data including volumetric imaging data,analyze the data to characterize the fissures, and display imagesincluding three-dimensional images of the fissures resulting from theanalysis of the imaging data on the visual display. The software may beincorporated into 3D pulmonary imaging software.

It should also be understood that the three-dimensional images or modelsdescribed herein are not truly created in three dimensions, because theyexist on a flat two-dimensional visual display. Rather, thethree-dimensional images described herein use perspective and shading,with the closest portions depicted in the foreground and more distantportions in the background, along with the ability of the user to rotatethe images in some cases and/or to see multiple views, to show theentire volumetric volume on the visual display. In contrast, each imagein the series of the multi-dimensional volumetric images provided by CTand MRI scans, for example, is a two-dimensional planar image thatdepicts the tissue present in a single plane or slice. These images aretypically acquired in three orthogonal planes, which are referred to asthe three orthogonal views and are typically identified as being axial,coronal and sagittal views.

Embodiments of the invention allow the clinician to interact with thethree-dimensional model of the lungs and the two-dimensional volumetricimages associated with and used to generate the model. For example, thethree-dimensional model and the associated two-dimensional volumetricimages may be presented in a graphical user interface on a visualdisplay. The user may interact with the graphical user interface, suchas by selecting a button, icon, and/or one or more locations on theimages or the model or elsewhere using a mouse, stylus, keypad,touchscreen or other type of interface known to those of skill in theart. The creation of the three-dimensional model may be performed by thesystem including a processor with software (computer readable media) toperform this function as well as software to permit a user to interactwith the graphical user interface, to calculate and display desired dataand images, and to perform the other functions described herein. Thesystem may further include the visual display on which the graphicaluser interface is displayed. The three-dimensional model andtwo-dimensional volumetric images may be provided to a user (such as aclinician or researcher) as a graphical user interface on a visualdisplay, which may be a computer screen, on which the images and datamay be manipulated by the user.

Examples of the embodiments may be implemented using a combination ofhardware, firmware, and/or software. For example, in many cases some orall of the functionality provided by examples may be implemented inexecutable software instructions capable of being carried on aprogrammable computer processor. Likewise, some examples of theinvention include a computer-readable storage device on which suchexecutable software instructions are stored. In certain examples, thesystem processor itself may contain instructions to perform one or moretasks. System processing capabilities are not limited to any specificconfiguration and those skilled in the art will appreciate that theteachings provided herein may be implemented in a number of differentmanners.

FIG. 1 shows a flowchart of a fissure characterization and visualizationmethod which may be carried out using software as part of a pulmonaryimaging system, for example. At step 1, volumetric radiological imagesor imaging data of a patient are transmitted to the pulmonary imagingsystem. Alternatively, the volumetric radiological images or imagingdata may already be stored within the memory of the system and may beaccessed by the processor. The volumetric radiological images or imagingdata may be CT scans, MRI scans, and/or PET scans, for example, fromwhich a series of two-dimensional planar images (referred to herein astwo-dimensional volumetric images or two-dimensional images) can beproduced in multiple planes, for example.

At step 2, the lungs, airways, and/or blood vessels are segmented usingthe 3D image data. The methods of performing lung, airway and vesselsegmentation from the volumetric images or imaging data may be thoseemployed by the Pulmonary Workstation of Vida Diagnostics, Inc.(Coralville, Iowa) and as described in the following references, each ofwhich is incorporated herein by reference: United States PatentPublication 2007/0092864, which is entitled: Treatment Planning Methods,Devices and Systems; United States Patent Publication 2006/0030958,which is entitled: Methods and Devices for Labeling and/or Matching;Tschirren et al., “Intrathoracic airway trees: segmentation and airwaymorphology analysis from low-dose CT scans,” IEEE Trans Med Imaging.2005 December; 24 (12):1529-39; Tschirren et al., “Matching andanatomical labeling of human airway tree,” IEEE Trans Med Imaging. 2005December; 24 (12):1540-7; Tschirren, Juerg, “Segmentation, AnatomicalLabeling, Branchpoint Matching, and Quantitative Analysis of HumanAirway Trees in Volumetric CT Images,” Ph.D. Thesis, The University ofIowa, 2003; Tschirren, Juerg, Segmentation, Anatomical Labeling,Branchpoint Matching, and Quantitative Analysis of Human Airway Trees inVolumetric CT Images, Slides from Ph.D. defense, The University of Iowa,2003; and Li, Kang, “Efficient Optimal Net Surface Detection for ImageSegmentation—From Theory to Practice,” M.Sc. Thesis, The University ofIowa, 2003, for example. Segmentation of the lungs, airways, and vesselsresults in identification of the lungs, airways, and vessels as distinctfrom the surrounding tissues and of separation of the lungs, airways,and vessels into smaller distinct portions which may be individuallyidentified in accordance with standard pulmonary anatomy.

At step 3, lobar segmentation is performed. The segmentation of thelungs, airways, and vessels obtained in step 2 can be used to identifyand delineate the lobes, again by applying standard pulmonary anatomy.For example, using the identified segments of the airway and/or vesseltrees obtained in step 2, the lobes may be segmented and identified byextracting the portions of the airway tree corresponding to particularlobes based on known air way tree structures and connectivityinformation. The extracted lobar airway tree portions may be furtherdivided into portions corresponding to sub-lobes, again based on knownairway and/or vessel tree structure and connectivity information. Inthis way, the portions of the volumetric images corresponding to lobesand/or sub-lobes can be identified.

In step 4, the lobar fissures portions of the volumetric images areidentified by the system. The lobar fissures, as formed by the abuttingpleural lining of the lobes, can be seen radiologically on X-ray as wellas on two-dimensional, volumetric images such as CT scans. As revealedby the tissues lining the fissures. The fissures may be automaticallydetected by the system in the volumetric images using known methods orother methods. In some embodiments, identification of the lobar fissuresbegins with enhancing the fissures to ensure accurate detection. In someembodiments, Hessian-matrix or structure tensor based approaches may beused for identification and enhancement of the fissures, as described inA. F. et al., “Multiscale vessel enhancement filtering,” MICCAI. 1998;1496 (3):130-7, for example. The identified fissures may be enhanced andshown to the user on the volumetric image. An example of this is shownin FIG. 2, which is a sagittal CT scan 10 including enhanced fissurelines 12.

l In step 5, the fissures may be characterized. This may be accomplishedby combining the information about the lobar segmentation obtained instep 3 with the fissure identification obtained in step 4. The locationsat which the lobar regions abut each other may be used to identify thelocation where a fissure would normally be present. However, in someindividuals, portions of the fissure (the tissue lining the fissure) maybe absent. Therefore, the normal fissure locations as determined fromthe lobar anatomy can be compared to the actual fissure locationsidentified in step 4. If there is a location where a fissure wouldnormally be present as determined by the abutting lobe surfaces, but thefissure identification indicated that there was no fissure present in aportion of or all of that location, then the fissure is described asmissing, absent or incomplete in that location. In this way, thepulmonary imaging system not only can identify and highlight existingfissures for users and present them in two-dimensional images andthree-dimensional models, but can also identify locations where thefissure is absent. The extent and location of absent fissures can thenbe used to characterize the patient's disease and to determineappropriate therapeutic approaches. This method differs from existingmethods in which absent portions are calculated by either fitting theexisting portions of the fissures to a reference atlas (van Rikxoort etal, 2011) or by an extrapolation of the existing portion of the fissureto the absent portion (Pu, et al., 2010). In the lobar atlas approach, areference atlas is created using the fissure locations of a group ofsubjects. The fissures of an individual patient can be compared to thereference atlas to predict the locations of absent portions of thefissures. This method relies on consistency of anatomy amongindividuals, which may not be accurate, particularly in the presence ofsevere disease which can dramatically change fissure patterns. In theextrapolation based method, the location of missing fissures isestimated by extending existing fissures into the missing spaces. Thismethod may cause unpredictable errors, particularly in patients havinglow fissure completeness. Therefore, although these and otheralternative methods of identifying missing fissures may be used, theseother approaches do not make full use of the anatomic informationavailable in the CT image data in the way that the identification ofabutting fissures does.

Once the locations of existing fissures and absent fissures have beenidentified, they can be presented visually to a user in two dimensions,such as on a CT scan, or in three dimensions, such as in athree-dimensional model. This step of fissure visualization is indicatedat step 6 on FIG. 1. In some embodiments, the visual presentations caneither show only the existing fissures, with gaps where the fissures areabsent. In other embodiments, only the areas of missing fissure may beshown. In still other embodiments, the areas of missing fissures can beshown, with the missing fissure being shown as the way the fissure wouldlook if it were present. In some embodiments, the missing fissure isshown in a way that contrasts with the existing fissure, to clearlyindicate that, although a fissure is shown, the displayed fissureactually represents an area of missing fissure. For example, the missingfissure portions may be shown in a different color than the existingfissure portions. The fissures may be shown as a three-dimensional modelin isolation or in combination with other components of the lungs suchas the airway tree, parenchyma, and/or the vessels.

An example of a three-dimensional model of a patient's fissures 30 inisolation is shown in FIG. 3, with the existing fissure portions 32shown in a first color represented by dark gray and the missing fissureportions 34 shown in a second color represented by light gray. In thispatient, who suffers from emphysema, the left oblique fissure 36 is morethan 95% complete, while the horizontal fissure 38 is only about 70%complete.

In FIG. 4 b, the existing 42 and missing portions 42, 44 of a patient'sfissures are shown in two dimensions, overlaid on a sagittal view CTimage 20 of the right lung of a patient. The existing fissures 42 areshown in a first color represented by dark gray, while the missingportions 44 are shown in a second color represented by white. Forpurposes of comparison, the same CT image is shown in FIG. 4 a withoutthe fissure overlay. It can be appreciated how much more difficult it isto determine the location of the fissures, and what portions are absent,without the assistance of the fissure visualization provided in FIG. 4b.

FIG. 5 is an example of fissure visualization in multiple views, as itmay be presented to a user in a graphical user interface and thereforerepresents a screen shot 50 that may be provided by the pulmonaryimaging system. It can be seen that the screenshot 50 includes CT images20 in the three orthogonal views: a sagittal view, an axial view, and atransverse view. In each of the CT images 20, the existing and missingportions of the fissures 42, 44 are enhanced using a different color,with a first color represented by dark gray indicating the existingfissure 42 and a second color represented by white indicating themissing fissure 44. The user may have the option to select differentimages to be presented on the display, such as by moving from one imageto another in a series for a particular view. The screenshot 50 alsoincludes a three-dimensional model of the fissures 30 along with a modelof the airway tree 60, constructed from the analysis of thetwo-dimensional volumetric data, with the areas existing and missingfissures 62, 64 shown in different colors corresponding to the colorsused in the two dimensional images and represented by dark gray andlight gray for purposes of visualization in this figure.

In addition to using the fissure information to visually enhance ordisplay the fissures, the fissure information can also be used tocharacterize the fissures, as indicated at step 5 of FIG. 1. Suchfissure characterization can include characterizing the location ofdisease, disease heterogeneity, and/or extent of disease (such as theGlobal Initiative for Chronic Lung Disease, or GOLD, classificationsystem), for example.

In some embodiments, a fissure integrity score may be calculated tocharacterize the fissure of a portion thereof The fissure integrityscore may be calculated as the incompleteness percentage (IP) orconversely as the completeness percentage (CP). These values may becalculated using the total area of existing fissure and of the absentfissure portions determined as described above using the followingequations:

IP(%)=100*[1−ExistingFissure/(ExistingFissure+AbsentFissure)]

CP(%)=100*ExistingFissure/(ExistingFissure+AbsentFissure)

These measurements can be made for a single fissure, for a selectedportion of a fissure such as only a portion abutting a particular lobeor sub-lobe, or for a combination of fissures or selected portions offissures. The choice of which portion of the fissure to assess may bedetermined by the possible locations of therapeutic interventions suchas BLVR surgery. That is, the fissure integrity score may be calculatedfor those fissures or portions thereof which abut a lobe or sub-lobe forwhich BLVR therapy is being considered. For example, if bronchoscopyguided BLVR therapy is being considered for either the left upper lobeor the left lower lobe, the fissure integrity score may be calculatedfor the entire left oblique fissure, because this fissure abuts both ofthese lobes along its entire length. If the use of BLVR therapy is beingconsidered in the right lower lobe, the fissure integrity score may becalculated based on the entire right oblique fissure. If BLVR surgery isbeing considered for the right upper lobe, the fissure integrity scoremay be calculated from the combination of the upper part of the obliquefissure (only the portion of the fissure abutting the right upper lobe)and the entire horizontal fissure. If BLVR surgery is being consideredfor the right middle lobe, the fissure integrity score may be calculatedfor a combination of the lower part of the oblique fissure (only theportion of the fissure abutting the right middle lobe) and the entirehorizontal fissure.

Because the fissure integrity score provides a numerical assessment ofhow intact (or not intact) the fissures are, it provides a globalquantitative assessment of possible collateral ventilation. For example,if the completeness percentage is 100%, the fissure is intact and thereis likely no collateral ventilation between adjacent lobes. BLVR therapyis therefore more likely to be successful. On the other hand, of thefissure integrity score indicates that the fissure completeness is low,collateral ventilation may occur through the missing areas of fissureand the outcome of BLVR therapy may be less successful.

In some embodiments, the fissure integrity score may be used to decidewhether or not to proceed with BLVR therapy and in which lobes orsub-lobes to perform such therapy. For example, a fissure integrityscore cut-off or threshold may be used for therapeutic decision making Apatient with a completeness percentage below the threshold may beineligible for BLVR surgery for the corresponding portion of the lung.Likewise a patient with an incompleteness percentage above the thresholdmay be ineligible for BLVR surgery for the corresponding portion of thelung. The fissure integrity score may therefore be used to triagepatients as being ineligible for, or possibly eligible for, BLVRtherapy.

In some embodiments, the relationship between the existing and absentfissures and other normal or abnormal lung structures can also beevaluated and measured. For example, the lobes of the human lungs can befurther dived into bronchopulmonary segments, also called sub-lobes.Each sub-lobe is supplied by one bronchus. There are typically 10sub-lobes in the right lung (3 in upper lobe, 2 in middle lobe, 5 inlower lobe) and 8-10 sub-lobes in the left lung (4-5 in upper lobe, 4-5in lower lobe). Depending on their locations, the surfaces of somesub-lobes may be located at fissure locations, thus contacting thefissures at such locations, or they may not abut the fissures. In someembodiments, the portion of a fissure contacting a sub-lobe may beidentified and characterized as separate from the remainder of thefissure. For example, characterization of a fissure in a sub-lobecontacting area can be performed (such as the completeness percent orthe incompleteness percent) and the portions of fissures in contact withdifferent sub-lobes can be visually distinguished from each other whendisplayed for user.

A visual presentation of the portions of fissures which contact varioussub-lobes can be provided to clinicians as an indication of the fissureintegrity at a sub-lobar level. An example of this is shown in FIGS. 6(a)-(d) in which 3 dimensional models of portions of a fissure are shownin a variety of ways that such models may be provided to a clinician,with the sub-lobe labels having been identified and displayed with thefissure portions based on the sub-lobe associated with (contacting) thatportion of the fissure. In these figures, the portions of the fissurescontacting different sub-lobes are each colored differently, representedby different shades of gray in the figures, in order to distinguish themfrom each other, and different colors are also used to distinguishexisting from missing fissure portions. In FIG. 9( a) the existingportions 62 left oblique fissure 70 are shown in dark gray while theabsent portions 64 shown in light gray. In FIG. 6( b), the left obliquefissure 70 is again shown, with each area of contact of the sub-lobes 76of the left upper lobe with the fissure distinctly colored and labeled.Similarly, in FIG. 6( c), the left oblique fissure is shown (as seenfrom below, the opposite side as shown in FIG. 6( b)) with each area ofcontact of the sub-lobes 78 of the left lower lobe distinctly coloredand labeled. In FIG. 6( d), the entire left lung is shown as athree-dimensional model 83, with each of the sub-lobes 82 separately anddistinctly colored (shown in shades of gray) and labeled with a sub-lobelabel 84 and with the fissure completeness score 86 for each portion ofthe fissure in contact with that sub-lobe.

This information relating to the completeness percentage of the portionof a fissure contacting a sub-lobe may be used in combination with otherinformation, such as density based emphysema measurements, which may bespecific to the lobes or sub-lobes, for example, to guide BLVR treatmentplanning This sub-lobe fissure information can then be used as a degreeof the influence of fissure integrity on sub-lobes. If treatment isbeing planned for a particular lung volume such as a lobe or sub-lobe,and if a portion of the fissure contact with that lung volume has a lowfissure integrity, the treatment of that lung volume may not beeffective or may be less effective than desired due to collateralventilation from across the fissure. In such cases, the treatment planmay be modified to manage the portion of the fissure having low fissureintegrity. For example, the treatment plan may include targetedtreatment of the particular lung volume as well as a sub-lobe orsub-lobes on the contralateral side of the fissure from the particularlung volume and adjacent to the portion of the fissure having lowfissure integrity. In this way, collateral ventilation of the particulartreated lung volume can be prevented by targeted treatments to lunglobes or sublobes across from each other on both sides of a portion ofthe fissure having low fissure integrity.

Other useful information which can be determined based on the fissureidentification includes the spatial relationship between fissurelocations and the regions of the lung affected by emphysema, forexample. For example, the distance of fissures (both intact and missingportions) from the centroids of regions of emphysema can be calculated.The orientation of the fissures relative to the regions of emphysema canalso be determined. This distance and orientation information can beused to predict the impact of fissure integrity on treatments in thecorresponding regions of emphysema. Additionally, the information mayhelp with characterizing the emphysema and understanding the impact offissure integrity on the progress of the emphysema.

FIG. 7 is an example of a visual representation of the spatialrelationship between fissures 70 and regions of emphysema as it may beprovided to a clinician in various embodiments. The visualrepresentation can be used by the clinician to visually assess the localinfluence of emphysema on fissure integrity. In FIG. 7, the regions ofemphysema are symbolically represented by spheres 90 with radiireflecting the sizes of those regions, though other types of visualrepresentations may alternatively be used.

Other information which can be determined using the fissureidentification includes the spacial relationship between fissures andtumors, which may have an impact on patient prognosis. For example,recent findings suggest that the presence of tumor invasion through afissure has a significant negative impact on long-term survival, dueperhaps to the rapid spread of such tumors. Thus, it is useful to knowthe relative locations of fissures and tumors, the distance betweenthem, and whether or not the tumors invade the fissures. Variousembodiments therefore identify the locations of tumors and fissures,provide images such as the 3 dimensional model of the fissures 70 andairways tree 60 shown in FIG. 8 in which the tumor 92, fissures 70, andthe airway tree 60 can be seen, and/or calculate the nearest distancebetween the fissures 70 and the tumor 92. Since tumors invading throughthe fissures have a significant effect on long-term survival, it isimportant to visualize the spatial relationship between fissures andtumors. In the example shown in FIG. 8, it can be seen that both tumors92 are confined to a single lobe and they do not invade the fissures 70.

In addition, local and global measurement of fissure integrity can alsobe utilized to predict the spread of diseases such as cancerous tumors.Other measurements which may be made by the system in variousembodiments include the distance between the fissures and anatomicallandmarks or locations such as the lung apex, the diaphragm, and theribs, for example. In addition, these measurements can be performed atdifferent levels of lung inflation, to provide information about, and tohelp better understand, lung mechanics in both normal and diseasedlungs.

As discussed above, the fissures are the interface between the lobes ofthe lungs and they are lined by the pleura. An analysis of the fissurescan therefore include characterization of the pleura itself. Forexample, pleural thickening can occur in certain disease conditions, andin some cases is due to inflammation. Such pleural thickening can resultin changes in the intensity distributions and thickness of fissuresurface. For example, portions of the fissure may have an abnormalintensity on volumetric imaging which may be indicative of the presenceof disease or fluid. Various embodiments may therefore identify theintensity, such as in Hounsfield Units (HU), of the fissures and of thevarious portions of the fissures if the intensity is not uniform.Various embodiments may therefore provide measurements of the intensitydistribution and the thickness of the pleura, or can assist a clinicianin making these measurements, to provide further information about andcharacterization of the associated disease.

In some embodiments, the shape of the fissure may be determined by thesystem. Fissure shape can be changed due to lung disease, such asemphysema. Thus, analysis of fissure shape can also be useful incharacterizing lung disease. The shape analysis may include, but is notlimited to, principal component analysis and surface curvaturemeasurement, for example. These results may be provided in comparison tonormal results, for example, to help identify areas of abnormality sincethe normal shape can be altered due to some diseases.

In some embodiments, the topology of the fissure surface may becharacterized. The topological information may include, for example, thenumber of holes (incomplete portions) in the fissure, which could becaused by or associated with a vein crossing the fissure.

In some embodiments, a clinician may interact with the visual display toidentify the fissures manually or to edit the fissures that wereautomatically identified by the system. An example of an editing toolicon 94 is shown in FIG. 9, in which a sagittal CT image 20 of the lungsis shown. The editing tool 94 can be used to edit the enhanced fissureline 22, such as to change the characterization of the identifiedfissure from existing fissure 42 to incomplete fissure 44 or vice versa.The editing tool, the icon for which may appear differently from thatshown in FIG. 9, may allow a user to change the identification of thevoxels at the fissure location, relabeling them as either existingfissure or incomplete/missing fissure.

In some embodiments, the process of editing a fissure using a fissureediting tool may include the following steps. First, a user may select afissure editing tool for use in a two-dimensional image. Thetwo-dimensional image may include identification of the fissurelocations as existing or incomplete, as automatically identified by thesystem, which may be shown enhancing the fissure by using colors such asblue for existing and green for missing fissure. The user may thenposition to the editing tool icon at a selected a location in thetwo-dimensional image including the automatically identified existingand missing fissure. The user may then direct the system to change thefissure identification (from existing to incomplete, or from complete toexisting) using the tool. For example, the user may click and drag amouse to move the corresponding tool icon on the display, at thelocation of the portion of the fissure for which the user wishes tochange the fissure identification. During use, the tool editing icon mayappear in a color matching the color of the new (revised) state of thefissure, such as a first color or shade of gray such as light gray forintact or a second color or shade of gray such as dark gray for missingfissure, for better visualization of the underlying CT data. The fissurelabel (existing or missing) in the edited image and neighboring imageswill be automatically updated according to the size of the 3D sphere. Anexample of this is shown in FIG. 9 in which circle 96 represents thecentral cross-section of the 3-dimensional volume within which thefissure identification will be changed, if so directed by the user. Thecolor change may occur immediately while the user is interacting withthe image, or may occur when the user indicates that editing iscomplete, such as by unclicking the mouse.

Fissure editing may also be performed by a user by interacting with athree-dimensional model of the fissures produced by the system. Anexample of this is shown in FIG. 10, in which the editing tool icon 94is shown in the 3D model of the fissures 30. The model also includes a3D model of the airway tree 60. The user may edit the fissurecharacterization using the following steps. First, the user may selectthe editing tool for use in the three-dimensional model, which displaysboth existing and incomplete portions 62, 64 of the fissures asautomatically identified by the system and/or previously edited by auser. The user may place the editing tool icon 94 on a selected locationon the fissure model 30. The user may then apply the tool to the fissureto change the identification of the fissure location as existing orincomplete, such as by clicking and dragging the icon using a mouse, atthe fissure location as described above for editing the two-dimensionalimage. In response, the system may change the fissure characterization,and likewise change the fissure color shown in the model 30, to indicatethe revised fissure characterization.

The use of the pulmonary visualization system which includes automaticlobar fissure identification, visualization, and characterization asdescribed herein provides several advantages. The system may provide apriori knowledge to predict the response of a patient to abronchoscopically-guided procedure such as an BLVR procedure. It mayalso provide an easily recognizable visual display of completeness andincompleteness of the lobar fissure, such as through the use of colorcoding. It may also provide an easily recognizable visual display of thespatial relationships between fissures and normal and abnormal lungstructures including the airway tree, the lobes, the sub-lobes, thefissures, regions of emphysema, and tumors, for example. In addition, itmay detect and identify normal and abnormal regions of the lungs andfissures and link two-dimensional data and images to multidimensionalvisualization and measurements. In some embodiments, it may offer“on-demand” measurement of fissures for purpose of immediate evaluationof normal and diseased states, determination of the appropriateness of aproposed procedure, and procedure planning The automation of themeasurement of the fissure integrity may provide enhanced clinicalutility by allowing easier, faster, and more accurate decisions, therebysaving time, money and potentially lives.

Various embodiments may be used by physicians to predict the response ofa patient with emphysema or other lung disease to a proposed procedure,such as the implantation of a device or other BLVR treatment. Treatmentplanning and determination of the most appropriate device therapy may beoptimized by predicting response. For example, thoracic surgeons may usethe information for treatment planning for lung volume reductionsurgery. Radiologists and pulmonary clinicians may use thesecharacterizations to determine the appropriate patients to triage toendobronchial BLVR therapy. Pulmonary clinicians may use the informationto plan procedures for BLVR therapies and to evaluate treatmentresponse.

In the foregoing detailed description, the invention has been describedwith reference to specific embodiments. However, it may be appreciatedthat various modifications and changes can be made without departingfrom the scope of the invention.

1. A system for visualizing pulmonary fissures of a person's lungscomprising; a processor; software comprising instructions for theprocessor for creating a visual display comprising the 3 dimensionalmodel of the pulmonary fissures, wherein creating a visual displaycomprising a 3 dimensional model of the pulmonary fissures comprises:accessing volumetric imaging data of the person's lungs; analyzing thevolumetric imaging data to segment the lungs into lobes; using thesegmented lobes, identifying locations at which pulmonary fissuresshould be present as the locations where the lobes abut each other;analyzing the volumetric images to identify locations at which pulmonaryfissures are present as existing fissure, comparing the identifiedlocations at which pulmonary fissures should be present to theidentified locations at which pulmonary fissures are present to identifylocations of missing fissure; and creating a visual display comprising a3 dimensional model of the pulmonary fissures comprising existingfissure portions and missing fissure portions, wherein the existingfissure portions are visually distinct from the missing fissureportions.
 2. The system of claim 1 wherein the existing fissure portionsare displayed in a different color than the missing fissure portions inthe 3 dimensional model.
 3. The system of claim 2 wherein the softwarefurther comprises instructions to create a graphical user interfaceallowing a user to reclassify a location on the 3-dimension model of thefissure from existing to missing or from missing to existing byinteracting with the 3 dimensional model on the graphical userinterface.
 4. The system of claim 2 wherein the 3 dimensional model ofthe fissures further comprises a 3 dimensional representation of thelung parenchyma in combination with the fissures.
 5. The system of claim2 wherein the 3 dimensional model of the fissures further comprises a 3dimensional representation of a tumor in combination with the fissures,wherein the software further comprises instructions for identifying alocation of the tumor by analyzing the volumetric imaging data.
 6. Thesystem of claim 5 wherein the software further includes instructions tocalculate a distance between the tumor and a nearest fissure location.7. The system of claim 1 wherein the software further comprisesinstructions for calculating a numerical value representing integrity ofthe fissures.
 8. The system of claim 7 wherein the numerical valueprovides a relative proportion of amount of the fissures that isexisting and amount of the fissures that is missing.
 9. The system ofclaim 7 wherein the software further comprises instructions forcalculating a numerical value representing integrity of a portion of afissure abutting a lobe, wherein the portion of the fissure abutting thelobe is less than all of the fissure.
 10. The system of claim 7 whereinthe software further comprises instructions for calculating a numericalvalue representing integrity of a portion of a fissure abutting asub-lobe.
 11. The system of claim 1 wherein the software furthercomprises instructions for receiving directions from a user toreclassify a fissure location identified by the system as existingfissure to be identified and displayed as missing fissure in the 3dimensional model.
 12. A system for visualizing pulmonary fissures of apatient's lungs comprising; a processor; software comprisinginstructions for the processor for creating a visual display comprisingthe 3 dimensional model of the pulmonary fissures, wherein creating avisual display comprising a 3 dimensional model of the pulmonaryfissures comprises: accessing volumetric imaging data of the patient'slungs; analyzing the volumetric imaging data to segment the lungs intolobes and sub-lobes; using the segmented lobes, identifying locations atwhich pulmonary fissures should be present where the lobes abut eachother; analyzing the volumetric images to identify locations at whichpulmonary fissures are present; comparing the identified locations atwhich pulmonary fissures should be present to the identified locationsat which pulmonary fissures are present to identify locations of missingfissure; identifying portions of the present and missing fissures whichabut the sub-lobes; and creating a visual display comprising a 3dimensional model of the pulmonary fissures comprising existing fissureportions and missing fissure portions, wherein the existing fissureportions are visually distinct from the missing fissure portions andwherein the portions of the missing and existing fissures abutting thesub-lobes are visually distinct from each other.
 13. The system of claim12 wherein the existing fissure portions are displayed in a differentcolor than the missing fissure portions in the 3 dimensional model. 14.The system of claim 12 wherein the portions of the missing and existingfissures abutting the sub-lobes are each presented in a different color.15. The system of claim 12 wherein the software further comprisesinstructions for calculating a numerical value representing integrity ofthe fissures, wherein the numerical value provides a relative proportionof amount of the fissures that is existing and amount of fissure that ismissing.
 16. The system of claim 15 wherein the numerical valuerepresenting integrity of the fissures is a calculation for theintegrity of an entire fissure, of only a portion abutting a lobe, oronly a portion of a fissure abutting a sub-lobe, wherein selection ofthe entire fissure, the portion abutting the lobe, or the portionabutting a sub-lobe can be determined by a user.
 17. The system of claim12 wherein the software further comprises instructions for receivingdirections from a user interacting with the 3 dimensional model of thefissures on a graphical user interface to reclassify a fissure locationidentified by the system as existing fissure to be identified anddisplayed as missing fissure, and to reclassify a fissure locationidentified by the system as missing fissure to be identified anddisplayed as existing fissure.
 18. A method for creating a threedimensional model of pulmonary fissures of a patient comprising:accessing volumetric imaging data of the patient's lungs; analyzing thevolumetric imaging data to segment the lungs into lobes; using thesegmented lobes, identifying locations at which pulmonary fissuresshould be present as the locations where the lobes abut each other;analyzing the volumetric images to identify locations at which pulmonaryfissures are present as existing fissure, comparing the identifiedlocations at which pulmonary fissures should be present to theidentified locations at which pulmonary fissures are present to identifylocations of missing fissure, and displaying the three dimensional modelon a display, wherein the visual display comprises existing fissureportions and missing fissure portions, wherein the existing fissureportions are visually distinct from the missing fissure portions. 19.The method of claim 18 further comprising calculating a numerical valuerepresenting integrity of the fissures, wherein the numerical valueprovides a relative proportion of amount of the fissures that isexisting and amount of fissure that is missing.
 20. The method of claim18 further comprising receiving directions from a user interacting withthe three dimensional model of the fissures to reclassify a fissurelocation identified by the system as existing fissure to be identifiedand displayed as missing fissure, and to reclassify a fissure locationidentified by the system as missing fissure to be identified anddisplayed as existing fissure.